Red eyes in dogs are a very common concern for pet owners, and it’s a symptom that can stem from a wide array of issues. From simple irritants and dryness to more serious underlying diseases, redness in your dog’s eyes is a sign of inflammation that shouldn’t be ignored. If you’ve noticed your dog’s eyes are red, particularly around the outside edges, it’s natural to be worried and want to understand what’s happening.
Redness indicates that something is irritating or inflaming the delicate structures of your dog’s eye. This inflammation can affect different parts of the eye, and the location and type of redness can provide clues about the potential cause. While sometimes it might be a minor issue, red eyes can also signal severe conditions that could lead to vision loss or even be life-threatening if left untreated. The intensity of the redness isn’t always a reliable indicator of the seriousness of the problem, making prompt veterinary attention crucial.
If you observe redness in your dog’s eyes, especially if it’s around the outside, it’s imperative to consult your veterinarian as quickly as possible. Early diagnosis and intervention are key to managing the underlying cause and protecting your dog’s eyesight.
Identifying Types of Redness in Your Dog’s Eyes
When we talk about “red eyes” in dogs, the redness can manifest in different ways, depending on which part of the eye is affected. Understanding these distinctions can help you better describe the issue to your vet and understand potential diagnoses. Here are the primary types of red eye appearances in dogs:
Episcleral Injection: Redness in the White of the Eye
The sclera, commonly known as the white of the eye, is the tough, protective outer layer. Episcleral injection occurs when the blood vessels within the sclera become enlarged and congested. Instead of their normal winding appearance, these vessels become straighter and more prominent, leading to redness. This type of redness is often described as being deeper and more intense.
Episcleral injection, even though visible on the outer eye, is typically a sign of disease inside the eye (intraocular disease). Conditions like uveitis (inflammation of the middle layer of the eye) or glaucoma (increased pressure inside the eye) can trigger this type of redness. If you notice this deep redness in the white part of your dog’s eye, it’s a strong indicator of a potentially serious internal eye problem.
Conjunctival Hyperemia: Redness of the Conjunctiva
The conjunctiva is a thin, transparent membrane that covers the sclera near the front of the eye and also lines the inner surface of the eyelids. Conjunctival hyperemia is the engorgement of blood vessels within this conjunctiva. When these vessels become congested and dilated, they cause increased redness, often appearing as bright red and can be more pronounced around the outer edges of the eye where the conjunctiva is most visible. This is often what people mean when they describe redness “around the outside” of their dog’s eyes.
Unlike episcleral injection, conjunctival hyperemia is usually associated with conditions affecting the outside of the eye (extraocular diseases). Common causes include conjunctivitis (inflammation of the conjunctiva, often called “pink eye” in humans), allergies, and environmental irritants. This type of redness is typically more superficial and can be accompanied by discharge.
Subconjunctival Hemorrhage: Diffuse Redness Covering the White of the Eye
Subconjunctival hemorrhage occurs when blood vessels beneath the conjunctiva rupture and bleed. This results in a diffuse, bright red discoloration that can cover a significant portion or even the entire white part of the eye. The blood vessels themselves are often obscured by the pooled blood, creating a solid red appearance.
This type of redness can be caused by trauma, such as excessive straining, injury, clotting disorders, or even forceful pulling on a leash. While it looks alarming, subconjunctival hemorrhage is often less indicative of serious internal eye disease than episcleral injection, but it still warrants veterinary attention to determine the underlying cause and rule out any complications.
Corneal Neovascularization: Redness Due to New Blood Vessel Growth on the Cornea
The cornea is the clear front surface of the eye. Corneal neovascularization refers to the formation of new blood vessels on the cornea in response to damage or oxygen deprivation. These new vessels appear as red lines or a reddish haze on the normally transparent cornea. The redness can be superficial, deep, localized, or spread across the entire cornea.
Corneal neovascularization is typically a response to corneal injury, such as scratches, ulcers, or inflammatory conditions like keratitis (corneal inflammation). It can also occur in association with intraocular diseases like glaucoma and uveitis as the cornea attempts to heal or respond to changes within the eye.
Hyphema: Blood Inside the Anterior Chamber
Hyphema is the presence of blood within the anterior chamber of the eye, the space between the cornea and the iris (the colored part of the eye). This type of redness can appear as a uniform red coloring in the anterior chamber or as a distinct red line or layer, depending on the amount of blood.
Hyphema can result from trauma, clotting disorders, uveitis, or systemic hypertension (high blood pressure). It’s a serious sign and requires prompt veterinary attention to identify the cause and prevent potential complications, including vision loss.
Alongside redness, other symptoms can accompany eye issues and provide further clues. These include:
- Third-eyelid inflammation: Swelling or redness of the nictitating membrane (the third eyelid in the corner of the eye).
- Eye discharge: Abnormal discharge, which can be clear, mucus-like, yellow, or green.
- Ruptured blood vessels: Visible broken blood vessels, particularly in subconjunctival hemorrhage.
- Swelling: Swelling in or around the eye area.
- Pain or discomfort: Signs of pain, such as pawing at the eye, rubbing the face, or squinting.
What Should You Do If Your Dog Has Red Eyes?
If you notice any redness in your dog’s eyes, a veterinary examination is crucial. A red eye is not a condition to wait and see about. Prompt evaluation is necessary to start appropriate medical treatment and safeguard your dog’s vision. Even if your dog seems otherwise well, eye issues can escalate quickly, and early intervention often leads to better outcomes.
Schedule an appointment with your veterinarian as soon as possible. Be prepared to describe the type of redness you’ve observed (e.g., around the outside, all over the white part, deep red, bright red), any accompanying symptoms, and when you first noticed the problem. This information will be helpful for your vet in making a diagnosis.
Common Causes of Red Eyes in Dogs
Many different conditions can lead to red eyes in dogs. Here are some of the most common causes:
Allergies
Just like humans, dogs can suffer from environmental allergies to substances like pollen, dust mites, mold, and dander. Allergic reactions can cause inflammation in the eyes, leading to redness, itching, and watery discharge. If your dog has seasonal allergies, you might notice red eyes flare up during certain times of the year.
Treatment for allergies depends on the cause and severity. It can include antihistamines (oral or topical), eye drops to manage inflammation and secondary infections, and in some cases, allergy testing and immunotherapy.
Conjunctivitis (“Pink Eye”)
Conjunctivitis, or inflammation of the conjunctiva, is a frequent cause of red eyes in dogs. It can be triggered by various factors, including viral or bacterial infections, allergies, foreign bodies in the eye, tear film disorders, and environmental irritants. Besides redness, conjunctivitis often presents with eye discharge, which can range from watery to thick and pus-like, depending on the cause.
Treatment typically involves topical medications like antibiotic or anti-inflammatory eye drops or ointments. In some cases, oral medications may be necessary, especially if there’s a systemic infection or underlying condition.
Keratoconjunctivitis Sicca (KCS) or “Dry Eye”
Keratoconjunctivitis Sicca (KCS), commonly known as dry eye, occurs when a dog doesn’t produce enough tears to properly lubricate and protect the eye’s surface. Without adequate tear production, the cornea and conjunctiva become irritated and inflamed, resulting in redness. Chronic dry eye can lead to corneal damage, pain, and vision problems.
KCS is often an immune-mediated condition and can be associated with other health issues like diabetes. Treatment usually involves a combination of medications to stimulate tear production (like cyclosporine or tacrolimus eye drops), artificial tears to provide lubrication, and antibiotics if secondary bacterial infections are present.
Entropion
Entropion is a condition where the eyelid rolls inward, causing the eyelashes and eyelid hair to rub against the surface of the eye. This constant irritation leads to corneal inflammation, pain, and redness. Entropion can be congenital (present from birth) or develop later in life.
Entropion often causes chronic eye irritation and can lead to recurrent eye infections and corneal ulcers. Corrective surgery is typically required to resolve entropion and prevent further damage to the eye.
Cherry Eye
Cherry eye is a condition where the gland of the third eyelid prolapses or pops out of its normal position. This gland, located at the inner corner of the eye, becomes swollen and red, resembling a cherry – hence the name. Cherry eye can occur in one or both eyes and is more common in certain breeds.
Mild cases of cherry eye might respond to anti-inflammatory eye drops. However, surgical correction is often necessary to reposition the gland and preserve its tear-producing function.
Eye Injury or Trauma
Physical injury or trauma to the eye is a direct cause of redness. Foreign objects (like grass seeds, dirt, or debris), scratches, abrasions, or blunt force trauma can all lead to inflammation and redness. Chemical irritants, such as smoke or fumes, can also irritate the eyes.
Treatment for eye trauma depends on the severity and type of injury. It may involve flushing the eye, topical medications (antibiotics, pain relievers), and in more severe cases, oral pain medication or even surgery. Corneal ulcers are a common complication of eye trauma.
Corneal Ulcers
Corneal ulcers are open sores on the cornea’s surface. They are often caused by trauma, but can also be secondary to infections (bacterial, viral, fungal), dry eye, or other eye diseases. Corneal ulcers are painful and cause significant redness, discharge, and squinting.
Corneal ulcers require prompt and aggressive treatment to prevent complications like infection, deep corneal damage, and vision loss. Treatment usually involves topical antibiotic eye drops or ointments, pain management, and sometimes surgery, depending on the ulcer’s depth and cause.
Glaucoma
Glaucoma is a condition characterized by increased pressure inside the eye (intraocular pressure). This elevated pressure damages the optic nerve and can lead to blindness. Glaucoma can be primary (inherited) or secondary to other eye diseases like uveitis or lens luxation. Redness is a common symptom of glaucoma, along with pain, cloudiness of the cornea, and dilated pupils.
Glaucoma is a serious condition that requires immediate veterinary intervention. Treatment aims to reduce intraocular pressure and can include topical and systemic medications, and often surgery.
Uveitis
Uveitis is inflammation of the uvea, the middle layer of the eye, which includes the iris, ciliary body, and choroid. Uveitis can be caused by infections, systemic diseases, trauma, toxins, or tumors. Redness is a hallmark symptom of uveitis, often accompanied by pain (squinting), cloudiness of the eye, and sometimes decreased intraocular pressure.
Uveitis requires careful diagnosis to identify the underlying cause. Treatment typically involves topical and oral anti-inflammatory medications, pain relief, and addressing the primary cause if identified.
Blepharitis
Blepharitis is inflammation of the eyelids. It can be caused by allergies, infections (bacterial or fungal), parasites, or immune-mediated diseases. Symptoms include eyelid redness, swelling, itching, and sometimes discharge. Entropion can also contribute to blepharitis.
Treatment for blepharitis depends on the underlying cause and may include topical or oral antibiotics, anti-inflammatory medications, anti-parasitic treatments, or surgery to correct entropion.
Tumors
Eye tumors, both benign and malignant, can develop in or around the eye and can cause redness. Tumors can lead to inflammation, pressure, and distortion of eye structures, resulting in redness and other symptoms depending on the tumor’s location and size.
Treatment for eye tumors varies widely depending on the type and extent of the tumor. Options can include surgery, radiation therapy, chemotherapy, or a combination of these.
High Blood Pressure (Systemic Hypertension)
High blood pressure in dogs can sometimes cause blood vessels in the eye to rupture, leading to subconjunctival hemorrhage and a very red eye. Untreated high blood pressure can have serious consequences, including blindness.
If high blood pressure is suspected, your veterinarian will need to diagnose and manage the underlying cause, which may involve medications to lower blood pressure.
How Veterinarians Diagnose the Cause of Red Eyes in Dogs
To determine the cause of your dog’s red eyes, your veterinarian will take a thorough approach, starting with a detailed medical history and a complete physical examination, with a focus on the eyes.
Diagnostic procedures commonly used include:
- Schirmer Tear Test: This test measures tear production to diagnose dry eye (KCS). A small paper strip is placed in the corner of the eye to assess tear volume.
- Fluorescein Stain: A harmless dye is applied to the cornea, and then the eye is examined with a special blue light. This stain helps to highlight any corneal abrasions, scratches, or ulcers, as the stain will adhere to damaged areas of the cornea.
- Tonometry: This procedure measures the intraocular pressure inside the eye. It’s essential for diagnosing glaucoma (high pressure) and uveitis (sometimes associated with low pressure).
In some cases, more advanced diagnostic testing may be necessary to identify the root cause of red eyes, such as:
- Ocular Ultrasound: Used to visualize the internal structures of the eye, particularly useful when the cornea is cloudy or there’s internal bleeding, helping to identify tumors, retinal detachments, or other internal abnormalities.
- Blood Pressure Monitoring: To check for systemic hypertension, especially if subconjunctival hemorrhage or other signs suggest high blood pressure.
- Advanced Imaging (CT Scan or MRI): In complex cases or when tumors are suspected, CT scans or MRIs can provide detailed images of the eye and surrounding tissues to help with diagnosis and treatment planning.
- Laboratory Tests: Blood work (chemistry profile, complete blood count, electrolyte panel) and urinalysis are often recommended to screen for underlying systemic diseases like infections, metabolic disorders, or clotting problems that could be contributing to the eye issue.
Treatment Options for Red Eyes in Dogs
Treatment for red eyes in dogs is highly dependent on the underlying cause. It’s crucial to follow your veterinarian’s specific recommendations.
In the meantime, while you are waiting for veterinary care, you can take a few steps for symptomatic relief:
- Cold Compress: Applying a cold compress with a soft, damp cloth to the affected eye can help reduce inflammation and provide temporary comfort.
- Avoid Irritants: Minimize exposure to potential irritants like smoke, dust, pollen, and strong fumes.
- Pet-Specific Eye Wash or Artificial Tears: If your dog tolerates it, you can use a sterile, pet-specific eye wash to gently flush the eye or artificial tear eye drops to lubricate the eye and soothe irritation, especially if dry eye is suspected. However, these are only for temporary relief and should not replace veterinary treatment.
It’s important to reiterate that red eyes can be a sign of a serious problem, and prompt veterinary attention is essential. In some cases, especially with conditions like glaucoma or corneal ulcers, red eyes can be considered a medical emergency, and immediate veterinary care is critical to prevent vision loss.
By understanding the potential causes and types of red eyes in dogs, you can be a proactive pet owner and seek timely veterinary care, ensuring the best possible outcome for your furry friend’s eye health.
WRITTEN BY
Barri J. Morrison, DVM
Veterinarian
